This is our time: Developing accurate and inclusive medical devices

Sensitive light-based wearable devices

Vincent Zoutenbier focuses on the interaction between light and human tissues. 'Light can be used as a very sensitive tool to measure important health indicators. For example, I work on projects aimed at using light to non-invasively check blood haemoglobin levels by shining light in the eye and to check your heart health by seeing how light reflects from the skin.’ Creating sensitive light-based wearable devices that detect conditions earlier is important because it can help medical professionals begin treatment before more severe symptoms begin. It is crucial for developing devices that aid in disease prevention and diagnosis.

Simulating tissue

Describing how light moves through tissue is a challenging topic. To help understand this, Vincent has developed a Python-based software package that allows TNO to digitally simulate the path light takes through tissue. These simulations are validated on artificial tissue materials, called phantom tissues, which mimic how light travels through skin and retinal layers (see model eye in photo).

'With measurements from physical phantom tissues and computer simulations of diverse tissues, we can create algorithms to find measurable differences between healthy and unhealthy tissue. Because it’s all virtual, we can even quantify signal changes due to normal variations due to age, skin colour, gender, and so on which vary from person to person. With this information, we can calibrate medical devices for more accurate biomarker detection through the whole population.

The power of light

Many current measurement methods rely on taking a sample and therefore produce single-use hazardous biological waste, much of which must be incinerated. 'Using light is much more comfortable for the patient since there are no needles or swabs and doesn’t require any single-use sampling materials.'

Accuracy and inclusivity

Conventional measurements of blood oxygen levels using fingertip devices can be significantly less accurate on patients with darker skin tone. Vincent is determined to change this. 'I don’t want anyone to have to wonder whether a medical measurement device is made for them or not. Every human body is different, but the physics behind light-based measurements is always the same. Our simulations acknowledge this and work to enable the engineering of inclusive and equitable devices.'

Uncharted territory

Much of what Vincent and his team work on is uncharted scientific territory, making it difficult to find existing literature to support simulation models. Questions such as ‘how much blood does each retinal layer contain?’ are easy to ask but difficult to answer.

'With every simulation I do, I gain more detailed anatomical knowledge... and more of those kinds of tricky questions come up. To answer them, we use TNO’s large research network to collaborate with medical and technological experts within TNO, as well as in hospitals around the world, to create models that push the boundaries of human physiological knowledge. To give an idea of the scope of our projects, we work with a Swedish ophthalmic device company on developing a new model eye, TNO Leiden and Holst Centre colleagues on measuring cardiovascular health, and even the Dutch Air Force.'

Building a toolbox

Vincent played a significant role in building up the light simulation capability at TNO by professionalising the tissue simulation package: Tissue Optics Monte Carlo Analysis (TOMCA). This flexible package makes measurements reproducible, traceable, and efficient and contains a database with literature references for all decisions and information about each device and tissue model.